contrib/libc++/include/tuple

   1 // -*- C++ -*-
   2 //===--------------------------- tuple ------------------------------------===//
   3 //
   4 //                     The LLVM Compiler Infrastructure
   5 //
   6 // This file is distributed under the University of Illinois Open Source
   7 // License. See LICENSE.TXT for details.
   8 //
   9 //===----------------------------------------------------------------------===//
  10
  11 #ifndef _LIBCPP_TUPLE
  12 #define _LIBCPP_TUPLE
  13
  14 /*
  15     tuple synopsis
  16
  17 namespace std
  18 {
  19
  20 template <class... T>
  21 class tuple {
  22 public:
  23     constexpr tuple();
  24     explicit tuple(const T&...);
  25     template <class... U>
  26         explicit tuple(U&&...);
  27     tuple(const tuple&) = default;
  28     tuple(tuple&&) = default;
  29     template <class... U>
  30         tuple(const tuple<U...>&);
  31     template <class... U>
  32         tuple(tuple<U...>&&);
  33     template <class U1, class U2>
  34         tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2
  35     template <class U1, class U2>
  36         tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2
  37
  38     // allocator-extended constructors
  39     template <class Alloc>
  40         tuple(allocator_arg_t, const Alloc& a);
  41     template <class Alloc>
  42         tuple(allocator_arg_t, const Alloc& a, const T&...);
  43     template <class Alloc, class... U>
  44         tuple(allocator_arg_t, const Alloc& a, U&&...);
  45     template <class Alloc>
  46         tuple(allocator_arg_t, const Alloc& a, const tuple&);
  47     template <class Alloc>
  48         tuple(allocator_arg_t, const Alloc& a, tuple&&);
  49     template <class Alloc, class... U>
  50         tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);
  51     template <class Alloc, class... U>
  52         tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);
  53     template <class Alloc, class U1, class U2>
  54         tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
  55     template <class Alloc, class U1, class U2>
  56         tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);
  57
  58     tuple& operator=(const tuple&);
  59     tuple&
  60         operator=(tuple&&) noexcept(AND(is_nothrow_move_assignable<T>::value ...));
  61     template <class... U>
  62         tuple& operator=(const tuple<U...>&);
  63     template <class... U>
  64         tuple& operator=(tuple<U...>&&);
  65     template <class U1, class U2>
  66         tuple& operator=(const pair<U1, U2>&); // iff sizeof...(T) == 2
  67     template <class U1, class U2>
  68         tuple& operator=(pair<U1, U2>&&); //iffsizeof...(T) == 2
  69
  70     void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));
  71 };
  72
  73 const unspecified ignore;
  74
  75 template <class... T> tuple<V...>  make_tuple(T&&...);
  76 template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept;
  77 template <class... T> tuple<T&...> tie(T&...) noexcept;
  78 template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls);
  79
  80 // 20.4.1.4, tuple helper classes:
  81 template <class T> class tuple_size; // undefined
  82 template <class... T> class tuple_size<tuple<T...>>;
  83 template <intsize_t I, class T> class tuple_element; // undefined
  84 template <intsize_t I, class... T> class tuple_element<I, tuple<T...>>;
  85
  86 // 20.4.1.5, element access:
  87 template <intsize_t I, class... T>
  88     typename tuple_element<I, tuple<T...>>::type&
  89     get(tuple<T...>&) noexcept;
  90 template <intsize_t I, class... T>
  91     typename tuple_element<I, tuple<T...>>::type const&
  92     get(const tuple<T...>&) noexcept;
  93 template <intsize_t I, class... T>
  94     typename tuple_element<I, tuple<T...>>::type&&
  95     get(tuple<T...>&&) noexcept;
  96
  97 // 20.4.1.6, relational operators:
  98 template<class... T, class... U> bool operator==(const tuple<T...>&, const tuple<U...>&);
  99 template<class... T, class... U> bool operator<(const tuple<T...>&, const tuple<U...>&);
 100 template<class... T, class... U> bool operator!=(const tuple<T...>&, const tuple<U...>&);
 101 template<class... T, class... U> bool operator>(const tuple<T...>&, const tuple<U...>&);
 102 template<class... T, class... U> bool operator<=(const tuple<T...>&, const tuple<U...>&);
 103 template<class... T, class... U> bool operator>=(const tuple<T...>&, const tuple<U...>&);
 104
 105 template <class... Types, class Alloc>
 106   struct uses_allocator<tuple<Types...>, Alloc>;
 107
 108 template <class... Types>
 109   void
 110   swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y)));
 111
 112 }  // std
 113
 114 */
 115
 116 #include <__config>
 117 #include <__tuple>
 118 #include <cstddef>
 119 #include <type_traits>
 120 #include <__functional_base>
 121 #include <utility>
 122
 123 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 124 #pragma GCC system_header
 125 #endif
 126
 127 _LIBCPP_BEGIN_NAMESPACE_STD
 128
 129 // allocator_arg_t
 130
 131 struct _LIBCPP_TYPE_VIS allocator_arg_t { };
 132
 133 #if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_MEMORY)
 134 extern const allocator_arg_t allocator_arg;
 135 #else
 136 constexpr allocator_arg_t allocator_arg = allocator_arg_t();
 137 #endif
 138
 139 // uses_allocator
 140
 141 template <class _Tp>
 142 struct __has_allocator_type
 143 {
 144 private:
 145     struct __two {char __lx; char __lxx;};
 146     template <class _Up> static __two __test(...);
 147     template <class _Up> static char __test(typename _Up::allocator_type* = 0);
 148 public:
 149     static const bool value = sizeof(__test<_Tp>(0)) == 1;
 150 };
 151
 152 template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
 153 struct __uses_allocator
 154     : public integral_constant<bool,
 155         is_convertible<_Alloc, typename _Tp::allocator_type>::value>
 156 {
 157 };
 158
 159 template <class _Tp, class _Alloc>
 160 struct __uses_allocator<_Tp, _Alloc, false>
 161     : public false_type
 162 {
 163 };
 164
 165 template <class _Tp, class _Alloc>
 166 struct _LIBCPP_TYPE_VIS uses_allocator
 167     : public __uses_allocator<_Tp, _Alloc>
 168 {
 169 };
 170
 171 #ifndef _LIBCPP_HAS_NO_VARIADICS
 172
 173 // uses-allocator construction
 174
 175 template <class _Tp, class _Alloc, class ..._Args>
 176 struct __uses_alloc_ctor_imp
 177 {
 178     static const bool __ua = uses_allocator<_Tp, _Alloc>::value;
 179     static const bool __ic =
 180         is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
 181     static const int value = __ua ? 2 - __ic : 0;
 182 };
 183
 184 template <class _Tp, class _Alloc, class ..._Args>
 185 struct __uses_alloc_ctor
 186     : integral_constant<int, __uses_alloc_ctor_imp<_Tp, _Alloc, _Args...>::value>
 187     {};
 188
 189 #endif  // _LIBCPP_HAS_NO_VARIADICS
 190
 191 #ifndef _LIBCPP_HAS_NO_VARIADICS
 192
 193 // tuple_size
 194
 195 template <class ..._Tp>
 196 class _LIBCPP_TYPE_VIS tuple_size<tuple<_Tp...> >
 197     : public integral_constant<size_t, sizeof...(_Tp)>
 198 {
 199 };
 200
 201 // tuple_element
 202
 203 template <size_t _Ip, class ..._Tp>
 204 class _LIBCPP_TYPE_VIS tuple_element<_Ip, tuple<_Tp...> >
 205 {
 206 public:
 207     typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
 208 };
 209
 210 // __tuple_leaf
 211
 212 template <size_t _Ip, class _Hp, bool=is_empty<_Hp>::value
 213 #if __has_feature(is_final)
 214                                  && !__is_final(_Hp)
 215 #endif
 216          >
 217 class __tuple_leaf;
 218
 219 template <size_t _Ip, class _Hp, bool _Ep>
 220 inline _LIBCPP_INLINE_VISIBILITY
 221 void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
 222     _NOEXCEPT_(__is_nothrow_swappable<_Hp>::value)
 223 {
 224     swap(__x.get(), __y.get());
 225 }
 226
 227 template <size_t _Ip, class _Hp, bool>
 228 class __tuple_leaf
 229 {
 230     _Hp value;
 231
 232     __tuple_leaf& operator=(const __tuple_leaf&);
 233 public:
 234     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
 235              _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
 236        {static_assert(!is_reference<_Hp>::value,
 237               "Attempted to default construct a reference element in a tuple");}
 238
 239     template <class _Alloc>
 240         _LIBCPP_INLINE_VISIBILITY
 241         __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
 242             : value()
 243         {static_assert(!is_reference<_Hp>::value,
 244               "Attempted to default construct a reference element in a tuple");}
 245
 246     template <class _Alloc>
 247         _LIBCPP_INLINE_VISIBILITY
 248         __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
 249             : value(allocator_arg_t(), __a)
 250         {static_assert(!is_reference<_Hp>::value,
 251               "Attempted to default construct a reference element in a tuple");}
 252
 253     template <class _Alloc>
 254         _LIBCPP_INLINE_VISIBILITY
 255         __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
 256             : value(__a)
 257         {static_assert(!is_reference<_Hp>::value,
 258               "Attempted to default construct a reference element in a tuple");}
 259
 260     template <class _Tp,
 261               class = typename enable_if<is_constructible<_Hp, _Tp>::value>::type>
 262         _LIBCPP_INLINE_VISIBILITY
 263         explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
 264             : value(_VSTD::forward<_Tp>(__t))
 265         {static_assert(!is_reference<_Hp>::value ||
 266                        (is_lvalue_reference<_Hp>::value &&
 267                         (is_lvalue_reference<_Tp>::value ||
 268                          is_same<typename remove_reference<_Tp>::type,
 269                                  reference_wrapper<
 270                                     typename remove_reference<_Hp>::type
 271                                  >
 272                                 >::value)) ||
 273                         (is_rvalue_reference<_Hp>::value &&
 274                          !is_lvalue_reference<_Tp>::value),
 275        "Attempted to construct a reference element in a tuple with an rvalue");}
 276
 277     template <class _Tp, class _Alloc>
 278         _LIBCPP_INLINE_VISIBILITY
 279         explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
 280             : value(_VSTD::forward<_Tp>(__t))
 281         {static_assert(!is_lvalue_reference<_Hp>::value ||
 282                        (is_lvalue_reference<_Hp>::value &&
 283                         (is_lvalue_reference<_Tp>::value ||
 284                          is_same<typename remove_reference<_Tp>::type,
 285                                  reference_wrapper<
 286                                     typename remove_reference<_Hp>::type
 287                                  >
 288                                 >::value)),
 289        "Attempted to construct a reference element in a tuple with an rvalue");}
 290
 291     template <class _Tp, class _Alloc>
 292         _LIBCPP_INLINE_VISIBILITY
 293         explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
 294             : value(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
 295         {static_assert(!is_lvalue_reference<_Hp>::value ||
 296                        (is_lvalue_reference<_Hp>::value &&
 297                         (is_lvalue_reference<_Tp>::value ||
 298                          is_same<typename remove_reference<_Tp>::type,
 299                                  reference_wrapper<
 300                                     typename remove_reference<_Hp>::type
 301                                  >
 302                                 >::value)),
 303        "Attempted to construct a reference element in a tuple with an rvalue");}
 304
 305     template <class _Tp, class _Alloc>
 306         _LIBCPP_INLINE_VISIBILITY
 307         explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
 308             : value(_VSTD::forward<_Tp>(__t), __a)
 309         {static_assert(!is_lvalue_reference<_Hp>::value ||
 310                        (is_lvalue_reference<_Hp>::value &&
 311                         (is_lvalue_reference<_Tp>::value ||
 312                          is_same<typename remove_reference<_Tp>::type,
 313                                  reference_wrapper<
 314                                     typename remove_reference<_Hp>::type
 315                                  >
 316                                 >::value)),
 317        "Attempted to construct a reference element in a tuple with an rvalue");}
 318
 319     __tuple_leaf(const __tuple_leaf& __t) _NOEXCEPT_(is_nothrow_copy_constructible<_Hp>::value)
 320         : value(__t.get())
 321         {static_assert(!is_rvalue_reference<_Hp>::value, "Can not copy a tuple with rvalue reference member");}
 322
 323     template <class _Tp>
 324         _LIBCPP_INLINE_VISIBILITY
 325         explicit __tuple_leaf(const __tuple_leaf<_Ip, _Tp>& __t)
 326                            _NOEXCEPT_((is_nothrow_constructible<_Hp, const _Tp&>::value))
 327             : value(__t.get()) {}
 328
 329     template <class _Tp>
 330         _LIBCPP_INLINE_VISIBILITY
 331         __tuple_leaf&
 332         operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
 333         {
 334             value = _VSTD::forward<_Tp>(__t);
 335             return *this;
 336         }
 337
 338     _LIBCPP_INLINE_VISIBILITY
 339     int swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
 340     {
 341         _VSTD::swap(*this, __t);
 342         return 0;
 343     }
 344
 345     _LIBCPP_INLINE_VISIBILITY       _Hp& get()       _NOEXCEPT {return value;}
 346     _LIBCPP_INLINE_VISIBILITY const _Hp& get() const _NOEXCEPT {return value;}
 347 };
 348
 349 template <size_t _Ip, class _Hp>
 350 class __tuple_leaf<_Ip, _Hp, true>
 351     : private _Hp
 352 {
 353
 354     __tuple_leaf& operator=(const __tuple_leaf&);
 355 public:
 356     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
 357              _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) {}
 358
 359     template <class _Alloc>
 360         _LIBCPP_INLINE_VISIBILITY
 361         __tuple_leaf(integral_constant<int, 0>, const _Alloc&) {}
 362
 363     template <class _Alloc>
 364         _LIBCPP_INLINE_VISIBILITY
 365         __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
 366             : _Hp(allocator_arg_t(), __a) {}
 367
 368     template <class _Alloc>
 369         _LIBCPP_INLINE_VISIBILITY
 370         __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
 371             : _Hp(__a) {}
 372
 373     template <class _Tp,
 374               class = typename enable_if<is_constructible<_Hp, _Tp>::value>::type>
 375         _LIBCPP_INLINE_VISIBILITY
 376         explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
 377             : _Hp(_VSTD::forward<_Tp>(__t)) {}
 378
 379     template <class _Tp, class _Alloc>
 380         _LIBCPP_INLINE_VISIBILITY
 381         explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
 382             : _Hp(_VSTD::forward<_Tp>(__t)) {}
 383
 384     template <class _Tp, class _Alloc>
 385         _LIBCPP_INLINE_VISIBILITY
 386         explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
 387             : _Hp(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) {}
 388
 389     template <class _Tp, class _Alloc>
 390         _LIBCPP_INLINE_VISIBILITY
 391         explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
 392             : _Hp(_VSTD::forward<_Tp>(__t), __a) {}
 393
 394     template <class _Tp>
 395         _LIBCPP_INLINE_VISIBILITY
 396         explicit __tuple_leaf(const __tuple_leaf<_Ip, _Tp>& __t)
 397             _NOEXCEPT_((is_nothrow_constructible<_Hp, const _Tp&>::value))
 398             : _Hp(__t.get()) {}
 399
 400     template <class _Tp>
 401         _LIBCPP_INLINE_VISIBILITY
 402         __tuple_leaf&
 403         operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
 404         {
 405             _Hp::operator=(_VSTD::forward<_Tp>(__t));
 406             return *this;
 407         }
 408
 409     _LIBCPP_INLINE_VISIBILITY
 410     int
 411     swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
 412     {
 413         _VSTD::swap(*this, __t);
 414         return 0;
 415     }
 416
 417     _LIBCPP_INLINE_VISIBILITY       _Hp& get()       _NOEXCEPT {return static_cast<_Hp&>(*this);}
 418     _LIBCPP_INLINE_VISIBILITY const _Hp& get() const _NOEXCEPT {return static_cast<const _Hp&>(*this);}
 419 };
 420
 421 template <class ..._Tp>
 422 _LIBCPP_INLINE_VISIBILITY
 423 void __swallow(_Tp&&...) _NOEXCEPT {}
 424
 425 template <bool ...> struct __all;
 426
 427 template <>
 428 struct __all<>
 429 {
 430     static const bool value = true;
 431 };
 432
 433 template <bool _B0, bool ... _Bp>
 434 struct __all<_B0, _Bp...>
 435 {
 436     static const bool value = _B0 && __all<_Bp...>::value;
 437 };
 438
 439 // __tuple_impl
 440
 441 template<class _Indx, class ..._Tp> struct __tuple_impl;
 442
 443 template<size_t ..._Indx, class ..._Tp>
 444 struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
 445     : public __tuple_leaf<_Indx, _Tp>...
 446 {
 447     _LIBCPP_INLINE_VISIBILITY
 448     _LIBCPP_CONSTEXPR __tuple_impl()
 449         _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
 450
 451     template <size_t ..._Uf, class ..._Tf,
 452               size_t ..._Ul, class ..._Tl, class ..._Up>
 453         _LIBCPP_INLINE_VISIBILITY
 454         explicit
 455         __tuple_impl(__tuple_indices<_Uf...>, __tuple_types<_Tf...>,
 456                      __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
 457                      _Up&&... __u)
 458                      _NOEXCEPT_((__all<is_nothrow_constructible<_Tf, _Up>::value...>::value &&
 459                                  __all<is_nothrow_default_constructible<_Tl>::value...>::value)) :
 460             __tuple_leaf<_Uf, _Tf>(_VSTD::forward<_Up>(__u))...,
 461             __tuple_leaf<_Ul, _Tl>()...
 462             {}
 463
 464     template <class _Alloc, size_t ..._Uf, class ..._Tf,
 465               size_t ..._Ul, class ..._Tl, class ..._Up>
 466         _LIBCPP_INLINE_VISIBILITY
 467         explicit
 468         __tuple_impl(allocator_arg_t, const _Alloc& __a,
 469                      __tuple_indices<_Uf...>, __tuple_types<_Tf...>,
 470                      __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
 471                      _Up&&... __u) :
 472             __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a,
 473             _VSTD::forward<_Up>(__u))...,
 474             __tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)...
 475             {}
 476
 477     template <class _Tuple,
 478               class = typename enable_if
 479                       <
 480                          __tuple_constructible<_Tuple, tuple<_Tp...> >::value
 481                       >::type
 482              >
 483         _LIBCPP_INLINE_VISIBILITY
 484         __tuple_impl(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_constructible<_Tp, typename tuple_element<_Indx,
 485                                        typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
 486             : __tuple_leaf<_Indx, _Tp>(_VSTD::forward<typename tuple_element<_Indx,
 487                                        typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
 488             {}
 489
 490     template <class _Alloc, class _Tuple,
 491               class = typename enable_if
 492                       <
 493                          __tuple_convertible<_Tuple, tuple<_Tp...> >::value
 494                       >::type
 495              >
 496         _LIBCPP_INLINE_VISIBILITY
 497         __tuple_impl(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
 498             : __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, typename tuple_element<_Indx,
 499                                        typename __make_tuple_types<_Tuple>::type>::type>(), __a,
 500                                        _VSTD::forward<typename tuple_element<_Indx,
 501                                        typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
 502             {}
 503
 504     template <class _Tuple>
 505         _LIBCPP_INLINE_VISIBILITY
 506         typename enable_if
 507         <
 508             __tuple_assignable<_Tuple, tuple<_Tp...> >::value,
 509             __tuple_impl&
 510         >::type
 511         operator=(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_assignable<_Tp&, typename tuple_element<_Indx,
 512                                        typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
 513         {
 514             __swallow(__tuple_leaf<_Indx, _Tp>::operator=(_VSTD::forward<typename tuple_element<_Indx,
 515                                        typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...);
 516             return *this;
 517         }
 518
 519         _LIBCPP_INLINE_VISIBILITY
 520         __tuple_impl&
 521         operator=(const __tuple_impl& __t) _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
 522         {
 523             __swallow(__tuple_leaf<_Indx, _Tp>::operator=(static_cast<const __tuple_leaf<_Indx, _Tp>&>(__t).get())...);
 524             return *this;
 525         }
 526
 527     _LIBCPP_INLINE_VISIBILITY
 528     void swap(__tuple_impl& __t)
 529         _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 530     {
 531         __swallow(__tuple_leaf<_Indx, _Tp>::swap(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t))...);
 532     }
 533 };
 534
 535 template <class ..._Tp>
 536 class _LIBCPP_TYPE_VIS tuple
 537 {
 538     typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;
 539
 540     base base_;
 541
 542     template <size_t _Jp, class ..._Up> friend
 543         typename tuple_element<_Jp, tuple<_Up...> >::type& get(tuple<_Up...>&) _NOEXCEPT;
 544     template <size_t _Jp, class ..._Up> friend
 545         const typename tuple_element<_Jp, tuple<_Up...> >::type& get(const tuple<_Up...>&) _NOEXCEPT;
 546     template <size_t _Jp, class ..._Up> friend
 547         typename tuple_element<_Jp, tuple<_Up...> >::type&& get(tuple<_Up...>&&) _NOEXCEPT;
 548 public:
 549
 550     _LIBCPP_INLINE_VISIBILITY
 551     _LIBCPP_CONSTEXPR tuple()
 552         _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
 553
 554     _LIBCPP_INLINE_VISIBILITY
 555     explicit tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
 556         : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
 557                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
 558                 typename __make_tuple_indices<0>::type(),
 559                 typename __make_tuple_types<tuple, 0>::type(),
 560                 __t...
 561                ) {}
 562
 563     template <class _Alloc>
 564       _LIBCPP_INLINE_VISIBILITY
 565       tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
 566         : base_(allocator_arg_t(), __a,
 567                 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
 568                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
 569                 typename __make_tuple_indices<0>::type(),
 570                 typename __make_tuple_types<tuple, 0>::type(),
 571                 __t...
 572                ) {}
 573
 574     template <class ..._Up,
 575               typename enable_if
 576                       <
 577                          sizeof...(_Up) <= sizeof...(_Tp) &&
 578                          __tuple_convertible
 579                          <
 580                             tuple<_Up...>,
 581                             typename __make_tuple_types<tuple,
 582                                      sizeof...(_Up) < sizeof...(_Tp) ?
 583                                         sizeof...(_Up) :
 584                                         sizeof...(_Tp)>::type
 585                          >::value,
 586                          bool
 587                       >::type = false
 588              >
 589         _LIBCPP_INLINE_VISIBILITY
 590         tuple(_Up&&... __u)
 591             _NOEXCEPT_((
 592                 is_nothrow_constructible<
 593                     typename __make_tuple_indices<sizeof...(_Up)>::type,
 594                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
 595                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
 596                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
 597                     _Up...
 598                 >::value
 599             ))
 600             : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
 601                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 602                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 603                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 604                     _VSTD::forward<_Up>(__u)...) {}
 605
 606     template <class ..._Up,
 607               typename enable_if
 608                       <
 609                          sizeof...(_Up) <= sizeof...(_Tp) &&
 610                          __tuple_constructible
 611                          <
 612                             tuple<_Up...>,
 613                             typename __make_tuple_types<tuple,
 614                                      sizeof...(_Up) < sizeof...(_Tp) ?
 615                                         sizeof...(_Up) :
 616                                         sizeof...(_Tp)>::type
 617                          >::value &&
 618                          !__tuple_convertible
 619                          <
 620                             tuple<_Up...>,
 621                             typename __make_tuple_types<tuple,
 622                                      sizeof...(_Up) < sizeof...(_Tp) ?
 623                                         sizeof...(_Up) :
 624                                         sizeof...(_Tp)>::type
 625                          >::value,
 626                          bool
 627                       >::type =false
 628              >
 629         _LIBCPP_INLINE_VISIBILITY
 630         explicit
 631         tuple(_Up&&... __u)
 632             _NOEXCEPT_((
 633                 is_nothrow_constructible<
 634                     typename __make_tuple_indices<sizeof...(_Up)>::type,
 635                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
 636                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
 637                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
 638                     _Up...
 639                 >::value
 640             ))
 641             : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
 642                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 643                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 644                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 645                     _VSTD::forward<_Up>(__u)...) {}
 646
 647     template <class _Alloc, class ..._Up,
 648               class = typename enable_if
 649                       <
 650                          sizeof...(_Up) <= sizeof...(_Tp) &&
 651                          __tuple_convertible
 652                          <
 653                             tuple<_Up...>,
 654                             typename __make_tuple_types<tuple,
 655                                      sizeof...(_Up) < sizeof...(_Tp) ?
 656                                         sizeof...(_Up) :
 657                                         sizeof...(_Tp)>::type
 658                          >::value
 659                       >::type
 660              >
 661         _LIBCPP_INLINE_VISIBILITY
 662         tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
 663             : base_(allocator_arg_t(), __a,
 664                     typename __make_tuple_indices<sizeof...(_Up)>::type(),
 665                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 666                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 667                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 668                     _VSTD::forward<_Up>(__u)...) {}
 669
 670     template <class _Tuple,
 671               typename enable_if
 672                       <
 673                          __tuple_convertible<_Tuple, tuple>::value,
 674                          bool
 675                       >::type = false
 676              >
 677         _LIBCPP_INLINE_VISIBILITY
 678         tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
 679             : base_(_VSTD::forward<_Tuple>(__t)) {}
 680
 681     template <class _Tuple,
 682               typename enable_if
 683                       <
 684                          __tuple_constructible<_Tuple, tuple>::value &&
 685                          !__tuple_convertible<_Tuple, tuple>::value,
 686                          bool
 687                       >::type = false
 688              >
 689         _LIBCPP_INLINE_VISIBILITY
 690         explicit
 691         tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
 692             : base_(_VSTD::forward<_Tuple>(__t)) {}
 693
 694     template <class _Alloc, class _Tuple,
 695               class = typename enable_if
 696                       <
 697                          __tuple_convertible<_Tuple, tuple>::value
 698                       >::type
 699              >
 700         _LIBCPP_INLINE_VISIBILITY
 701         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
 702             : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
 703
 704     template <class _Tuple,
 705               class = typename enable_if
 706                       <
 707                          __tuple_assignable<_Tuple, tuple>::value
 708                       >::type
 709              >
 710         _LIBCPP_INLINE_VISIBILITY
 711         tuple&
 712         operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<base&, _Tuple>::value))
 713         {
 714             base_.operator=(_VSTD::forward<_Tuple>(__t));
 715             return *this;
 716         }
 717
 718     _LIBCPP_INLINE_VISIBILITY
 719     void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 720         {base_.swap(__t.base_);}
 721 };
 722
 723 template <>
 724 class _LIBCPP_TYPE_VIS tuple<>
 725 {
 726 public:
 727     _LIBCPP_INLINE_VISIBILITY
 728     _LIBCPP_CONSTEXPR tuple() _NOEXCEPT {}
 729     template <class _Alloc>
 730     _LIBCPP_INLINE_VISIBILITY
 731         tuple(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
 732     template <class _Alloc>
 733     _LIBCPP_INLINE_VISIBILITY
 734         tuple(allocator_arg_t, const _Alloc&, const tuple&) _NOEXCEPT {}
 735     template <class _Up>
 736     _LIBCPP_INLINE_VISIBILITY
 737         tuple(array<_Up, 0>) _NOEXCEPT {}
 738     template <class _Alloc, class _Up>
 739     _LIBCPP_INLINE_VISIBILITY
 740         tuple(allocator_arg_t, const _Alloc&, array<_Up, 0>) _NOEXCEPT {}
 741     _LIBCPP_INLINE_VISIBILITY
 742     void swap(tuple&) _NOEXCEPT {}
 743 };
 744
 745 template <class ..._Tp>
 746 inline _LIBCPP_INLINE_VISIBILITY
 747 typename enable_if
 748 <
 749     __all<__is_swappable<_Tp>::value...>::value,
 750     void
 751 >::type
 752 swap(tuple<_Tp...>& __t, tuple<_Tp...>& __u)
 753                  _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 754     {__t.swap(__u);}
 755
 756 // get
 757
 758 template <size_t _Ip, class ..._Tp>
 759 inline _LIBCPP_INLINE_VISIBILITY
 760 typename tuple_element<_Ip, tuple<_Tp...> >::type&
 761 get(tuple<_Tp...>& __t) _NOEXCEPT
 762 {
 763     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 764     return static_cast<__tuple_leaf<_Ip, type>&>(__t.base_).get();
 765 }
 766
 767 template <size_t _Ip, class ..._Tp>
 768 inline _LIBCPP_INLINE_VISIBILITY
 769 const typename tuple_element<_Ip, tuple<_Tp...> >::type&
 770 get(const tuple<_Tp...>& __t) _NOEXCEPT
 771 {
 772     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 773     return static_cast<const __tuple_leaf<_Ip, type>&>(__t.base_).get();
 774 }
 775
 776 template <size_t _Ip, class ..._Tp>
 777 inline _LIBCPP_INLINE_VISIBILITY
 778 typename tuple_element<_Ip, tuple<_Tp...> >::type&&
 779 get(tuple<_Tp...>&& __t) _NOEXCEPT
 780 {
 781     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 782     return static_cast<type&&>(
 783              static_cast<__tuple_leaf<_Ip, type>&&>(__t.base_).get());
 784 }
 785
 786 // tie
 787
 788 template <class ..._Tp>
 789 inline _LIBCPP_INLINE_VISIBILITY
 790 tuple<_Tp&...>
 791 tie(_Tp&... __t) _NOEXCEPT
 792 {
 793     return tuple<_Tp&...>(__t...);
 794 }
 795
 796 template <class _Up>
 797 struct __ignore_t
 798 {
 799     template <class _Tp>
 800         _LIBCPP_INLINE_VISIBILITY
 801         const __ignore_t& operator=(_Tp&&) const {return *this;}
 802 };
 803
 804 namespace { const __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); }
 805
 806 template <class _Tp> class _LIBCPP_TYPE_VIS reference_wrapper;
 807
 808 template <class _Tp>
 809 struct ___make_tuple_return
 810 {
 811     typedef _Tp type;
 812 };
 813
 814 template <class _Tp>
 815 struct ___make_tuple_return<reference_wrapper<_Tp> >
 816 {
 817     typedef _Tp& type;
 818 };
 819
 820 template <class _Tp>
 821 struct __make_tuple_return
 822 {
 823     typedef typename ___make_tuple_return<typename decay<_Tp>::type>::type type;
 824 };
 825
 826 template <class... _Tp>
 827 inline _LIBCPP_INLINE_VISIBILITY
 828 tuple<typename __make_tuple_return<_Tp>::type...>
 829 make_tuple(_Tp&&... __t)
 830 {
 831     return tuple<typename __make_tuple_return<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
 832 }
 833
 834 template <class... _Tp>
 835 inline _LIBCPP_INLINE_VISIBILITY
 836 tuple<_Tp&&...>
 837 forward_as_tuple(_Tp&&... __t) _NOEXCEPT
 838 {
 839     return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...);
 840 }
 841
 842 template <size_t _Ip>
 843 struct __tuple_equal
 844 {
 845     template <class _Tp, class _Up>
 846     _LIBCPP_INLINE_VISIBILITY
 847     bool operator()(const _Tp& __x, const _Up& __y)
 848     {
 849         return __tuple_equal<_Ip - 1>()(__x, __y) && get<_Ip-1>(__x) == get<_Ip-1>(__y);
 850     }
 851 };
 852
 853 template <>
 854 struct __tuple_equal<0>
 855 {
 856     template <class _Tp, class _Up>
 857     _LIBCPP_INLINE_VISIBILITY
 858     bool operator()(const _Tp&, const _Up&)
 859     {
 860         return true;
 861     }
 862 };
 863
 864 template <class ..._Tp, class ..._Up>
 865 inline _LIBCPP_INLINE_VISIBILITY
 866 bool
 867 operator==(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 868 {
 869     return __tuple_equal<sizeof...(_Tp)>()(__x, __y);
 870 }
 871
 872 template <class ..._Tp, class ..._Up>
 873 inline _LIBCPP_INLINE_VISIBILITY
 874 bool
 875 operator!=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 876 {
 877     return !(__x == __y);
 878 }
 879
 880 template <size_t _Ip>
 881 struct __tuple_less
 882 {
 883     template <class _Tp, class _Up>
 884     _LIBCPP_INLINE_VISIBILITY
 885     bool operator()(const _Tp& __x, const _Up& __y)
 886     {
 887         return __tuple_less<_Ip-1>()(__x, __y) ||
 888              (!__tuple_less<_Ip-1>()(__y, __x) && get<_Ip-1>(__x) < get<_Ip-1>(__y));
 889     }
 890 };
 891
 892 template <>
 893 struct __tuple_less<0>
 894 {
 895     template <class _Tp, class _Up>
 896     _LIBCPP_INLINE_VISIBILITY
 897     bool operator()(const _Tp&, const _Up&)
 898     {
 899         return false;
 900     }
 901 };
 902
 903 template <class ..._Tp, class ..._Up>
 904 inline _LIBCPP_INLINE_VISIBILITY
 905 bool
 906 operator<(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 907 {
 908     return __tuple_less<sizeof...(_Tp)>()(__x, __y);
 909 }
 910
 911 template <class ..._Tp, class ..._Up>
 912 inline _LIBCPP_INLINE_VISIBILITY
 913 bool
 914 operator>(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 915 {
 916     return __y < __x;
 917 }
 918
 919 template <class ..._Tp, class ..._Up>
 920 inline _LIBCPP_INLINE_VISIBILITY
 921 bool
 922 operator>=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 923 {
 924     return !(__x < __y);
 925 }
 926
 927 template <class ..._Tp, class ..._Up>
 928 inline _LIBCPP_INLINE_VISIBILITY
 929 bool
 930 operator<=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
 931 {
 932     return !(__y < __x);
 933 }
 934
 935 // tuple_cat
 936
 937 template <class _Tp, class _Up> struct __tuple_cat_type;
 938
 939 template <class ..._Ttypes, class ..._Utypes>
 940 struct __tuple_cat_type<tuple<_Ttypes...>, __tuple_types<_Utypes...> >
 941 {
 942     typedef tuple<_Ttypes..., _Utypes...> type;
 943 };
 944
 945 template <class _ResultTuple, bool _Is_Tuple0TupleLike, class ..._Tuples>
 946 struct __tuple_cat_return_1
 947 {
 948 };
 949
 950 template <class ..._Types, class _Tuple0>
 951 struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0>
 952 {
 953     typedef typename __tuple_cat_type<tuple<_Types...>,
 954             typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type>::type
 955                                                                            type;
 956 };
 957
 958 template <class ..._Types, class _Tuple0, class _Tuple1, class ..._Tuples>
 959 struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...>
 960     : public __tuple_cat_return_1<
 961                  typename __tuple_cat_type<
 962                      tuple<_Types...>,
 963                      typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type
 964                  >::type,
 965                  __tuple_like<typename remove_reference<_Tuple1>::type>::value,
 966                  _Tuple1, _Tuples...>
 967 {
 968 };
 969
 970 template <class ..._Tuples> struct __tuple_cat_return;
 971
 972 template <class _Tuple0, class ..._Tuples>
 973 struct __tuple_cat_return<_Tuple0, _Tuples...>
 974     : public __tuple_cat_return_1<tuple<>,
 975          __tuple_like<typename remove_reference<_Tuple0>::type>::value, _Tuple0,
 976                                                                      _Tuples...>
 977 {
 978 };
 979
 980 template <>
 981 struct __tuple_cat_return<>
 982 {
 983     typedef tuple<> type;
 984 };
 985
 986 inline _LIBCPP_INLINE_VISIBILITY
 987 tuple<>
 988 tuple_cat()
 989 {
 990     return tuple<>();
 991 }
 992
 993 template <class _Rp, class _Indices, class _Tuple0, class ..._Tuples>
 994 struct __tuple_cat_return_ref_imp;
 995
 996 template <class ..._Types, size_t ..._I0, class _Tuple0>
 997 struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, _Tuple0>
 998 {
 999     typedef typename remove_reference<_Tuple0>::type _T0;
1000     typedef tuple<_Types..., typename __apply_cv<_Tuple0,
1001                           typename tuple_element<_I0, _T0>::type>::type&&...> type;
1002 };
1003
1004 template <class ..._Types, size_t ..._I0, class _Tuple0, class _Tuple1, class ..._Tuples>
1005 struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>,
1006                                   _Tuple0, _Tuple1, _Tuples...>
1007     : public __tuple_cat_return_ref_imp<
1008          tuple<_Types..., typename __apply_cv<_Tuple0,
1009                typename tuple_element<_I0,
1010                   typename remove_reference<_Tuple0>::type>::type>::type&&...>,
1011          typename __make_tuple_indices<tuple_size<typename
1012                                  remove_reference<_Tuple1>::type>::value>::type,
1013          _Tuple1, _Tuples...>
1014 {
1015 };
1016
1017 template <class _Tuple0, class ..._Tuples>
1018 struct __tuple_cat_return_ref
1019     : public __tuple_cat_return_ref_imp<tuple<>,
1020                typename __make_tuple_indices<
1021                         tuple_size<typename remove_reference<_Tuple0>::type>::value
1022                >::type, _Tuple0, _Tuples...>
1023 {
1024 };
1025
1026 template <class _Types, class _I0, class _J0>
1027 struct __tuple_cat;
1028
1029 template <class ..._Types, size_t ..._I0, size_t ..._J0>
1030 struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J0...> >
1031 {
1032     template <class _Tuple0>
1033     _LIBCPP_INLINE_VISIBILITY
1034     typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type
1035     operator()(tuple<_Types...> __t, _Tuple0&& __t0)
1036     {
1037         return _VSTD::forward_as_tuple(_VSTD::forward<_Types>(get<_I0>(__t))...,
1038                                       get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
1039     }
1040
1041     template <class _Tuple0, class _Tuple1, class ..._Tuples>
1042     _LIBCPP_INLINE_VISIBILITY
1043     typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&, _Tuple1&&, _Tuples&&...>::type
1044     operator()(tuple<_Types...> __t, _Tuple0&& __t0, _Tuple1&& __t1, _Tuples&& ...__tpls)
1045     {
1046         typedef typename remove_reference<_Tuple0>::type _T0;
1047         typedef typename remove_reference<_Tuple1>::type _T1;
1048         return __tuple_cat<
1049            tuple<_Types..., typename __apply_cv<_Tuple0, typename tuple_element<_J0, _T0>::type>::type&&...>,
1050            typename __make_tuple_indices<sizeof ...(_Types) + tuple_size<_T0>::value>::type,
1051            typename __make_tuple_indices<tuple_size<_T1>::value>::type>()
1052                            (_VSTD::forward_as_tuple(
1053                               _VSTD::forward<_Types>(get<_I0>(__t))...,
1054                               get<_J0>(_VSTD::forward<_Tuple0>(__t0))...
1055                             ),
1056                             _VSTD::forward<_Tuple1>(__t1),
1057                             _VSTD::forward<_Tuples>(__tpls)...);
1058     }
1059 };
1060
1061 template <class _Tuple0, class... _Tuples>
1062 inline _LIBCPP_INLINE_VISIBILITY
1063 typename __tuple_cat_return<_Tuple0, _Tuples...>::type
1064 tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls)
1065 {
1066     typedef typename remove_reference<_Tuple0>::type _T0;
1067     return __tuple_cat<tuple<>, __tuple_indices<>,
1068                   typename __make_tuple_indices<tuple_size<_T0>::value>::type>()
1069                   (tuple<>(), _VSTD::forward<_Tuple0>(__t0),
1070                                             _VSTD::forward<_Tuples>(__tpls)...);
1071 }
1072
1073 template <class ..._Tp, class _Alloc>
1074 struct _LIBCPP_TYPE_VIS uses_allocator<tuple<_Tp...>, _Alloc>
1075     : true_type {};
1076
1077 template <class _T1, class _T2>
1078 template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2>
1079 inline _LIBCPP_INLINE_VISIBILITY
1080 pair<_T1, _T2>::pair(piecewise_construct_t,
1081                      tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
1082                      __tuple_indices<_I1...>, __tuple_indices<_I2...>)
1083     :  first(_VSTD::forward<_Args1>(get<_I1>( __first_args))...),
1084       second(_VSTD::forward<_Args2>(get<_I2>(__second_args))...)
1085 {
1086 }
1087
1088 #endif  // _LIBCPP_HAS_NO_VARIADICS
1089
1090 _LIBCPP_END_NAMESPACE_STD
1091
1092 #endif  // _LIBCPP_TUPLE